Fire a gun on the moon?

[JettaKnight]

That movie was fantastic. It completely lived up to the trailers for it.

What? How'd you see it?

 

[RobbyMaQ]

... On the moon, it might bounce you back a step, just because you're not held to the surface as hard, but it's not going to send you careening off into space.

Damn... Just once I'd like to careen

 

[mtgasten]

not sure if this has been posted yet, but isnt this why the GyroJet was made??

Gyrojet - Wikipedia, the free encyclopedia

 

[Scutter01]

What? How'd you see it?

I live in the Matrix.

 

[btownie]

Although gunpowder/cordite contains its own oxidizer I still don't think a flintlock would work due to the fact that the flint striking mechanism has no oxigen so I don't think it would provide a spark for the gun power in the flash pan. Anything percusion lock and later ought to work I think.

That was my thought process.

 

[Mr. Habib]

Here's another point to consider. Is there enough energy in a conventional primer to generate enough heat to start combustion of the powder in space? The military only tests ammo down to -60. BIG difference between that and the temps in space.

 

[AndersonIN]

Are there any astronauts on INGO willing to give this a go?

Would never get it past TSA!

 

[indyjoe]

Ballistics would be easier to calculate with little atmospheric resistance on the moon. It would be pure physics parabola, with no bullet velocity reduction.

This of course made me jump to the idea of if I could get a bullet fired from the moon to reach escape velocity (where it would not be pulled back by the gravity of the moon.)

Escape velocity on the moon would be 2.4 km/s, from the moon. However, escape velocity from the Earth AT the moon is around 1.4 km/s. So if you were firing from the moon towards the Earth, you would be about 1 km/s escape velocity. (Let the Earth gravity help pull the bullet away.)

So 1 km/s or about 3280 fps would be the slowest possible escape velocity to get a bullet to not return to the surface of the moon. With rifle shots that are over 4000 fps on Earth, it might be possible.

I wonder how much velocity gain you get from not forcing the 14.7 psi air out of the barrel in front of an accelerating projectile. Your moon rifle may need a slower twist for maximum accuracy.

 

[indyjoe]

Here's another point to consider. Is there enough energy in a conventional primer to generate enough heat to start combustion of the powder in space? The military only tests ammo down to -60. BIG difference between that and the temps in space.

Since there is almost no atmosphere in space, the temperature loss due to conduction is almost nill. Heat loss due to radiation is the smallest portion. I was trying to find some posts I have done on this at a site, but haven't been able to.

The simple way to think of it is this. Air that is humid takes much more energy to change the temperature than dry air. Because the air has much more thermal mass. This also means that it has much more energy to give off. Dry air at the temperature of steam will not do anywhere nears as good a job of burning you than steam itself, because steam has much more heat energy to transfer into your skin.

Now take this to space, where the pressure of the atmosphere is very close to zero. This means that even if it was -200 F, it would take a LONG time to influence the barrel temperature of a firearm down to that which would inhibit ignition. The atmosphere just has so little thermal energy compared to the thermal mass of the barrel. A much larger influence on temperature is solar radiation. This is also why we see such extreme temperatures in space, because the atmosphere doesn't have the thermal mass to limit the temperature swings.

On the shadow side of the moon, you would eventually reach a temperature that could inhibit ignition. I'm thinking it was somewhere on the order of hours, however. (If I'm remembering the calcs right.)

The bigger problem would be cooling if multiple shots were required. The heat that is normally dissipated into the air on Earth would have to be dissipated to an atmosphere that has very little capability of receiving it.

The black body radiation of heat energy from the gun barrel is only a small piece of the cooling required. At some point I think you could get an auto loading rifle to be hot enough to cook off and then essentially "run away" without user intervention.

I'm too far removed from Thermo class to calculate when this would be.

 

[Mr. Habib]

Assuming that the rounds are stored at normal earth temps, taken out and immediately fired, you're probably right. Allow the rounds to come to thermal equilibrium with their environment and I think that they probably won't fire. This should be easy to test. All we would need is a Dewar of LN that we could haul to a range and some ammo.

 

[indyjoe]

Assuming that the rounds are stored at normal earth temps, taken out and immediately fired, you're probably right. Allow the rounds to come to thermal equilibrium with their environment and I think that they probably won't fire. This should be easy to test. All we would need is a Dewar of LN that we could haul to a range and some ammo.

I would worry about the brittleness of the brass cartridge (and barrel as well) if cooled too far. Definitely not something I'd want to shoot without a Mythbusters style blast shield or distance. I'm not familiar with the change in characteristics of metals down near Liquid Nitrogen temps. Although it would probably be enough to shoot empty shells with just a primer in place, to test initial ignition.

Definitely would want to use dry lube though.

 

[Scutter01]

Don't forget: If it's exposed to any solar radiation, it's going to encounter some massively-uneven heating. One side of the pistol might become extremely hot while the other side stays ice cold.

 

[indyjoe]

Don't forget: If it's exposed to any solar radiation, it's going to encounter some massively-uneven heating. One side of the pistol might become extremely hot while the other side stays ice cold.

Not necessarily. I agree that solar radiation is going to affect the temperature of the gun. However, the thermal conductivity of the metal would be superior to the loss of temperature due to black body radiation on the shaded side. So I would think the temperatures would stay reasonably close for any parts with decent thermal conductivity.

I may not be as much of a Glock fan in space. What temp does the polymer melt, anyway?

 

[LEaSH]

wtf is going on here in this thread?

Oh, space bullets again. Cool.

Did you know that the dust on the moon acts as a great insulator because the dust is actually composed of nano strand-like particles? It can be scorching hot on the surface of the moon, but frozen solid less than a foot down! Amazing.

Space is far out.

"It is a bitter thing indeed, to be given awesomeness; and such received, worry only over the reductive pedantry of why."

-Sir Reginald Internet.

 

[armedindy]

i bet itd be fun to watch the spent shells go flying in low gravity

 

[btownie]

Since there is almost no atmosphere in space, the temperature loss due to conduction is almost nill. Heat loss due to radiation is the smallest portion. I was trying to find some posts I have done on this at a site, but haven't been able to.

The simple way to think of it is this. Air that is humid takes much more energy to change the temperature than dry air. Because the air has much more thermal mass. This also means that it has much more energy to give off. Dry air at the temperature of steam will not do anywhere nears as good a job of burning you than steam itself, because there is much more heat energy to transfer into your skin.

Now take this to space, where the pressure of the atmosphere is very close to zero. This means that even if it was -200 F, it would take a LONG time to influence the barrel temperature of a firearm down to that which would inhibit ignition. The atmosphere just has so little thermal energy compared to the thermal mass of the barrel. A much larger influence on temperature is solar radiation. This is also why we see such extreme temperatures in space, because the atmosphere doesn't have the thermal mass to limit the temperature swings.

On the shadow side of the moon, you would eventually reach a temperature that could inhibit ignition. I'm thinking it was somewhere on the order of hours, however. (If I'm remembering the calcs right.)

The bigger problem would be cooling if multiple shots were required. The heat that is normally dissipated into the air on Earth would have to be dissipated to an atmosphere that has very little capability of receiving it.

The black body radiation of heat energy from the gun barrel is only a small piece of the cooling required. At some point I think you could get an auto loading rifle to be hot enough to cook off and then essentially "run away" without user intervention.

I'm too far removed from Thermo class to calculate when this would be.

 

[Ted]

If Gerald Bull wasn't assassinated by the Israeli Mossad, I'm sure that he could have figured a way to fire a projectile to the moon.

 

[cobber]

With 1/6 the gravity, you'd have to re-zero your sights.

But isn't the Moon a Gun Free Zone?

 

[Ted]

With 1/6 the gravity, you'd have to re-zero your sights.

But isn't the Moon a Gun Free Zone?

No. There are FEMA camps and black helicopters there.